Do subagents burn your Claude Code limit faster?

A developer measured subagent token costs on a single Claude Code account over two days (23–25 October), finding that each subagent model call consumes roughly 0.07% of the 5-hour limit — about the same as a main-thread call. Subagents drain the limit through call volume rather than per-call cost: a typical subagent used about 1.9% of a 5-hour window, while the largest (86 calls) used 10.1%, and the costliest tenth of subagents accounted for 29% of all subagent usage. The findings were published alongside limitcast, a local-only CLI tool that forecasts when Claude Code, Codex and Grok usage limits will run out.

Subagents are the usual suspect when a Claude Code limit runs out early. I measured what they actually cost on my account, using the same fit as in How many tokens is 1% of your Claude Code limit? https://limitcast.dev/blog/tokens-per-percent/ Per model call, no. A subagent call cost about the same share of my 5-hour limit as a main-thread call: roughly 0.07%. Subagents burn the limit because of how many calls they make. A typical subagent cost about 2% of a 5-hour window, so five in parallel cost about 10%. Over two days 23–25 October , on one account: | | Model calls | New tokens per call | Cached tokens per call | Limit per call | Share of the limit used | |---|---|---|---|---|---| | Main thread | 4,234 | 6.6k | 353k | 0.072% | ≈ 60% | | Subagents | 2,895 | 8.4k | 223k | 0.071% | ≈ 40% | These two days end a few hours later than the ones in the first post, so its subagent share 42% and this one 40% differ slightly. The two cancel out. The main thread re-reads a bigger context on every call 353k cached tokens against 223k , but cached tokens count about 1/67 as much as new ones. Each subagent writes its own context into the cache from scratch, so its calls carry more new tokens 8.4k against 6.6k , and new tokens are what move the meter. The same two days had 93 subagents. Priced against the 5-hour limit: | Typical subagent median | 16 calls | ≈ 1.9% of a 5-hour window | | Average | | ≈ 2.3% | | 1 in 10 cost more than | | ≈ 4.1% | | Largest | 86 calls | ≈ 10.1% | The costliest tenth of subagents used 29% of everything subagents used. Most subagents are cheap; a few long ones are not, and a batch of them started at once is what ends a window early. npm install -g limitcast limitcast install records your limit readings from the status line use Claude Code for a day or two, then: limitcast results what moves your meter: new vs cached tokens limitcast report Pro: tokens by day, project, model and session, and the subagent share The free version is local-only and never uses your Claude login. Originally published at limitcast.dev https://limitcast.dev/blog/subagents/ . limitcast is a local-only command-line tool that forecasts when your Claude Code, Codex and Grok usage limits run out.